Authentication medium, authentication medium manufacturing method, authentication medium reading method, and authentication medium verification method

ABSTRACT

An authentication medium includes a sheet-like laminate sheet; a first region that is formed on the laminate sheet and where personal identification information is recorded; and a second region that is formed on the laminate sheet and has a hologram structure where check data associated with first individual information is recorded.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application is a continuation application filed under 35 U.S.C. §111(a) claiming the benefit under 35 U.S.C. §§ 120 and 365(c) ofInternational Patent Application No. PCT/JP2019/025868, filed on Jun.28, 2019, which is based upon and claims the benefit of priority toJapanese Patent Application No. 2018-124211, filed on Jun. 29, 2018 andJapanese Patent Application No. 2018-204306, filed on Oct. 30, 2018, thedisclosures of which are incorporated herein by reference in theirentireties.

TECHNICAL FIELD

Embodiments of the present invention relate to an authentication medium,an authentication medium manufacturing method, an authentication mediumreading method, and an authentication medium verification method.

BACKGROUND ART

As authentication media containing personal information, variousidentification (ID) cards such as passports and driver's licenses areknown. Most ID cards have facial images and character informationdisplayed thereon to visually identify personal information. However,personal information simply printed on an authentication medium isvulnerable to tampering and counterfeiting.

As a method of preventing counterfeiting of authentication media, PTL 1describes that the anti-tampering property of an authentication mediumis improved by transferring a hologram foil to the authenticationmedium.

PTL 2 describes the addition of personal information using a fluorescentlight-emitting material such that the personal information istransparent and cannot be visually recognized when observed undervisible light but can be visually recognized under ultravioletobservation.

The anti-counterfeiting technique described in PTL 1 is already wellknown and will permit easy counterfeiting of holograms emitting simpleiridescent diffraction light.

PTL 3 describes, as another anti-counterfeiting method, performingauthenticity verification using reproduction information displayed on ahologram by irradiating the hologram with light of a specificwavelength.

[Citation List][Patent Literatures] [PTL 1] JP-A-H6-67592; [PTL 2]JP-B-3198324; [PTL 3] JP-B-4677683.

SUMMARY OF THE INVENTION Technical Problem

In the technique described in PTL 3, the reproduction information ispreset and invariant. Thus, once a counterfeiter knows the reproductioninformation, they may produce a hologram imitating the reproductioninformation, so that this technique has still room for improvement.

Under the foregoing circumstances, embodiments of the present inventionaim to provide an authentication medium that helps deter tampering andcounterfeiting, using a simple configuration, and a technique related toverification.

Solution to Problem

The embodiments of the present invention are a group of embodimentsbased on a single unique invention from the background. The aspects ofthe present disclosure are those of the group of embodiments based on asingle invention. Configurations of the present disclosure can haveaspects of the present disclosure. As a solution according to presentinvention, embodiments of the present invention have aspects describedbelow. These aspects may be combined together, and the combinations canexert synergistic effects. The aspects can also be combined withfeatures of the embodiments, and the combinations can exert synergisticeffects. The features of the embodiments may be combined together, andthe combinations can exert synergistic effects.

A first aspect of the present invention is an authentication medium thatincludes: a sheet-like laminate sheet; a first region that is formed onthe laminate sheet and where first individual information is recorded;and a second region that is formed on the laminate sheet and has ahologram structure where second individual information associated withthe first individual information is recorded.

A second aspect of the present invention is an authentication mediummanufacturing method that includes: a step of acquiring first individualinformation; a step of generating second individual informationassociated with the first individual information; a step of recordingthe first individual information on a laminate sheet; and a step offorming a hologram structure where the second individual information isrecorded on the laminate sheet.

A third aspect of the present invention is an authentication mediumreading method for reading the authentication medium of the presentinvention.

This method includes: a step of acquiring condition informationindicating a condition for reproducing second individual information ona hologram structure of the authentication medium; and a step ofreproducing the second individual information by irradiating thehologram structure with light based on the condition information.

A fourth aspect of the present invention is an authentication mediumverification method for determining authenticity of the authenticationmedium of the present invention.

This method includes: a step of reading first individual informationrecorded on the authentication medium; a step of reading secondindividual information recorded on a hologram structure of theauthentication medium; and a step of determining authenticity of theauthentication medium based on the read first individual information andsecond individual information.

Advantageous Effects of Invention

According to the embodiments of the present invention, it is possible tohelp deter tampering and counterfeiting in a simple configuration.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view theoretically describing an authentication mediumaccording to an embodiment of the present invention.

FIG. 2A is a perspective view of the authentication medium.

FIG. 2B is a diagram theoretically describing reconstructed images in asecond region of the authentication medium.

FIG. 3 is a flowchart showing a method of manufacturing theauthentication medium according to the embodiment.

FIG. 4A is a perspective view conceptually explaining concepts of ahologram film for use in an embodiment of the present invention.

FIG. 4B is a cross-sectional view taken along line of FIG. 4A, whichconceptually explaining concepts of the positions of the reconstructedimages.

FIG. 5 is a flowchart describing a method of verifying theauthentication medium according to the embodiment.

FIG. 6 is a diagram showing an example of a hologram structure.

FIG. 7 is a diagram showing an example of a hologram structure.

FIG. 8 is a diagram showing an example of a hologram structure formedfrom a plurality of unit cell regions.

FIG. 9 is a diagram showing an example of a hologram structure formedfrom a plurality of unit cell regions.

FIG. 10 is a diagram showing an example of a hologram structure formedfrom a plurality of unit cell regions.

FIG. 11 is a diagram showing an example of a hologram structure fromwhich a reflective layer is omitted.

FIG. 12 is a diagram showing an example of a hologram structure fromwhich a reflective layer is omitted.

FIG. 13 is a diagram showing a hologram structure and reproductionpositions of reconstructed images.

FIG. 14 is a diagram showing an example of a hologram structure area ina unit cell region.

FIG. 15 is a diagram showing an example of a hologram structure regionfrom which a reflective layer is not completely omitted.

FIG. 16 is a diagram showing an example of a hologram structure area ina unit cell region.

FIG. 17 is a diagram showing an example of a hologram structure area ina unit cell region.

FIG. 18 is a diagram showing an example of a hologram structure area ina unit cell region.

FIG. 19 is a diagram showing an example of positional relationshipbetween a hologram structure and a reproduction position of areconstructed image.

FIG. 20 is a diagram showing an example of positional relationshipbetween a hologram structure and a reproduction position of areconstructed image.

DETAILED DESCRIPTION

Embodiments of the present invention of will be described below withreference to the drawings. In the following description of the drawingsto be referred, components or functions identical with or similar toeach other are given the same or similar reference signs, unless thereis a reason not to. It should be noted that the drawings are onlyschematically illustrated, and thus the relationship between thicknessand two-dimensional size of the components, and the thickness ratiobetween the layers, are not to scale. Therefore, specific thicknessesand dimensions should be understood in view of the followingdescription. As a matter of course, dimensional relationships or ratiosmay be different between the drawings.

Further, the embodiments described below are merely examples ofconfigurations for embodying the technical idea of the presentinvention. The technical idea of the present invention does not limitthe materials, shapes, structures, arrangements, and the like of thecomponents to those described below. The technical idea of the presentinvention can be modified variously within the technical scope definedby the claims. The present invention is not limited to the followingembodiments within the scope not departing from the spirit of thepresent invention.

In any group of successive numerical value ranges described in thepresent specification, the upper limit value or lower limit value of onenumerical value range may be replaced with the upper limit value orlower limit value of another numerical value range. In the numericalvalue ranges described in the present specification, the upper limitvalues or lower limit values of the numerical value ranges may bereplaced with values shown in examples. The configuration according to acertain embodiment may be applied to other embodiments

An embodiment of the present invention will be described below withreference to FIGS. 1 to 20 .

(Authentication Medium)

FIG. 1 is a plan view of an authentication medium 100 according to thepresent embodiment. The authentication medium 1 includes a sheet-likelaminate sheet 30, and a first region 11 and a second region 12 formedon portions of the laminate sheet 30.

The authentication medium 100 may be a laminate. The laminate can be acard or a page. The laminate can be made by laminating a plurality oflaminate sheets 30. The laminate sheet 30 can be a thermoplastic sheet.The material for the laminate sheet 30 can be polycarbonate or vinylchloride. The laminate can be a sheet-like laminate of polycarbonate ora sheet-like laminate of vinyl chloride. The lamination can be thermallamination. The card can be an ID card, a national ID card, a creditcard, a driver's license card, a residence card, or the like. The pagecan be a data page of a passport. The thickness of the page can be 0.5mm or more and 2.5 mm or less.

Personal identification information 21 of the authentication medium 100is recorded in the first region 11. The personal identificationinformation 21 can be the owner's personal identification information.The personal identification information can include information aboutthe owner of the card or a booklet. The personal identificationinformation is personal biometric information, personal non-biometricinformation, or a pair of them. The biometric information can bebiometric information from which a person can be identified. Thebiometric information allows biometric authentication. Instances ofnon-biometric information include name, birth date, country of origin,place of origin, and personal identification number. These can be acombination of characters, numbers, symbols, and the like. Instances ofpersonal biometric information include a facial image, fingerprintpattern, retina pattern, voice print, handwriting, and signature. Thepersonal identification information 21 is configured to be visuallyrecognizable under visible light such that identity of the person can beconfirmed visually.

The material for the laminate sheet 30 can be a thermoplastic. Thethermoplastic of the laminate sheet 30 can be a polycarbonate resin. Thepolycarbonate resin allows the personal identification information 21 tobe recorded by laser engraving. The personal identification information21 can be laser-printed by irradiating the laminate sheet 30 with laserlight and carbonizing the polycarbonate resin with heat from the laser.The personal identification information 21 can be recorded by modulatinga drawing position, drawing depth, drawing point, pulse width, pulsefrequency, pulse energy, laser irradiation intensity, or laserirradiation time, or a combination thereof, depending on the personalidentification information 21 to be recorded.

The method of recording the personal identification information 21 isnot limited to laser engraving. Instead of laser engraving, the personalidentification information 21 may be formed by printing on the laminatesheet 30. Alternatively, the personal identification information 21 maybe printed on a resin sheet different from the laminate sheet 30, andthe resin sheet may be attached to the laminate sheet 30 or embedded ina transparent laminate sheet.

When the personal identification information 21 is added to the surfaceor inside of the laminate sheet 30, if the authentication medium 100 isdestroyed for the purpose of counterfeiting or imitation, the personalidentification information 21 will also become corrupted, so that it canbe detected that an act of forging or counterfeiting has been performed.

A hologram structure is formed in the second region 12. As shown in FIG.2A, the hologram structure displays check data 22 generated from thepersonal identification information 21 as a reconstructed image. Thecheck data 22 is recorded on the hologram structure.

With the check data 22 recorded, the hologram structure may be formed soas to overlap the region where the personal biometric information isrecorded. That is, the hologram structure may be formed partially or inthe entire region where the personal biometric information is recorded.In this case, in the event of the biometric information being tamperedwith, the hologram structure becomes corrupted so that the diversion ofthe hologram structure can be prevented. In this configuration, thecheck data 22 may be generated from the personal non-biometricinformation. This facilitates prevention of impersonation by which thepersonal non-biometric information such as national origin and thebiometric information such as a facial image may be replaced withanother person's information.

The check data 22 may be generated from only the personal non-biometricinformation. This allows the check data 22 to be provided more easily.

The check data 22 is provided from the personal identificationinformation 21. The check data 22 can be provided by extracting aspecific portion of the personal identification information 21 as dataor by generating data using a predetermined algorithm from all or partof the personal identification information 21. Hash values may beobtained using a hash function from all or part of the personalbiometric information and be set as the check data 22. Otherwise, hashvalues may be obtained using a hash function from all or part of onlythe personal biometric information and be set as the check data. Thismakes it possible to detect tampering of the biometric information byusing the check data 22. In this configuration, the hologram structurewith the check data 22 recorded thereon may be formed so as to overlapthe region where the personal non-biometric information is recorded.That is, the hologram structure may be formed partially or in the entireregion where the personal biometric information is recorded. Thisprevents impersonation in which the personal non-biometric informationsuch as national origin and the biometric information such as a facialimage is replaced with another person's information.

The check data 22 can be digital data. The digital data may be a singleor multiple sets of the same numbers, alphabets, or characters invarious languages as a part of the personal identification information21. Otherwise, the digital data may be numbers, characters, or symbolsthat are obtained by converting all or some numbers or characters in thepersonal identification information 21 by using a function, matrix, oralgorithm. The digital data may be recorded as a code on the hologramstructure. The code can be a one-dimensional code or two-dimensionalcode. An instance of a one-dimensional code is a bar code. An instanceof a two-dimensional code is a QR code (registered trademark) or amatrix code.

The check data 22 can be hash values of a part or all of the personalidentification information 21. A simple hash function for generating thecheck data can be used to convert the characters and numbers included inthe personal identification information into ASCII codes and form anumber string, and divide the number string by a specific number stringand set the resulting remainder as the check data. Otherwise, specificinformation included in the personal identification information (forexample, a combination of the last two digits of the birth date and thecharacters of the first name, etc.) itself may be set as the check data.In this case, the size of the characters and numbers can be in the rangeof 10 μm or more and 300 μm or less. In this range, the check data canbe made incapable of visual recognition by the naked eye. Thesecharacters can be microtext. The size of the characters and numbers canbe in the range of 300 μm or more and 5 mm or less. In this range, thecheck data can be made capable of visual recognition by the naked eye.

The hash function for generating the hash values can be a cryptographichash function. As such a cryptographic hash function, the Secure HashAlgorithm or a block cipher standardized by the US National Institute ofStandards and Technology can be applied. Instances of the cryptographichash function include MDS, SHA family, Whirlpool, RIPEMD, RadioGatun,bcrypt, and BLAKE2.

The information amount of the check data 22 is smaller than theinformation amount of the personal identification information 21. Thebit number of the check data 22 can have a fixed length or a variablelength. The bit number of the check data 22 can be in the range of onebit or more and 1024 bits or less, and may be in the range of two bitsor more and 64 bits or less. In this range, the check data 22 can behandled more easily. When the number of bits of the check data 22 isvariable, the number of bits of the check data 22 can take a value inaccordance with the level of security required for the authenticationmedium. Since the hologram structure itself has security, one bit or twobits of check data may be sufficient in some cases. In addition, thenumber of bits may be small when the number of issued authenticationmedia is small, and the bit number may be sequentially increased with anincrease in the volume of issuance. By doing so, when residence cardsare applied as the authentication media, for example, it is possible tosequentially enhance the security in accordance with the number ofregistered foreigners. That is, it is possible to achieve scalablesecurity.

Various publicly known structures are applicable to the hologramstructure in the second region 12. Among them, a volume hologram inwhich the refractive index in a formative layer is modulated and asurface-relief hologram with a relief on its surface are suitable forthe hologram structure. The volume hologram can be a Lippmann hologram.The surface-relief hologram can be a computer-generated hologram. Thecomputer-generated hologram can be a kinoform. The computer-generatedhologram is a hologram formed by computing a diffraction gratinghologram pattern from a reconstructed image. A kinoform is obtained byrecording a phase on a kinoform of a reconstructed image to be recordedon the kinoform, as a phase difference on the surface of the kinoform. ALippmann hologram or a computer-generated hologram on which opticalphase information is recorded can be formed as a hologram film. A partof the hologram film on which optical phase information for display of areconstructed image is recorded can be transferred to a fixed positionon a card or a page. This allows the reconstructed image of the checkdata 22 to be reproduced at a position with accuracy.

The hologram structure in the second region 12 can be formed from aLippmann volume hologram by irradiating a light-responsive photopolymerwith object light from the preset check data and reference light forreproducing the object light and then recording its interference fringeson the photopolymer. Alternatively, the Lippmann volume hologram may beformed by computing in advance optical phase information of object lightfrom the check data such that the optical phase information is set asspatial distribution of a phase difference in a spatial light phasemodulator and that light having passed through or reflected on thespatial optical phase modulator is set as object light. The material forthe volume hologram can be a photopolymer of which the refractive indexis modulated by photosensitizing. The type of the photopolymer can be aphoto-crosslinking type or a photopolymerized type. An instance of thephoto-crosslinking type has polyvinyl carbazole as the main component.The photopolymerized type is highly sensitive due to a chain reactionduring photosensitization. With the photo-crosslinking type, it is easyto produce a large difference in refractive index. The photopolymerizedtype can be a wet type requiring development or a dry type not requiringdevelopment. A dry-type photopolymer can have a pair oflow-compatibility materials with different refractive indexes as themain components. An instance of the pair of main components is a pair ofa vinyl acetate compound and an acrylic acid ester compound, or a pairof an epoxy compound and an acrylic acid ester compound, either of whichmay be a polymer. A photopolymer having a vinyl acetate compound and anacrylic acid ester compound as the pair of main components can easilyproduce a difference in refractive index. A photopolymer having an epoxycompound and an acrylic acid ester compound as the pair of maincomponents can easily enhance durability. An instance of the wet type isa mixture of polyvinyl pyrrolidone and a monomer. This mixture hasportions with low light intensity that dissolve in the developer andleaves voids, and thus can easily produce a large difference inrefractive index. A volume hologram can be replicated by irradiating amaster hologram with a laser, and exposing the photopolymer tointerference fringes of the reflected light (object light) and theirradiating laser light (reference light) to modulate the refractiveindex of the photopolymer. (Contact copy method)

The hologram structure in the second region 12 can be formed from asurface-relief hologram using the procedure described below. Opticalphase information for forming the preset check data is specified. Theoptical phase information is recorded on a resist plate as the depth ofa fine concavo-convex structure by a laser lithography system or anelectron beam lithography system, or using an ion beam lithographicmethod. An embossed stamper is manufactured by electroforming with aresist plate as a master. A film is embossed and replicated using thisembossed stamper having the fine concavo-convex structure as a cylindermold, thereby obtaining the hologram film. The film to be embossed mayhave a carrier and a relief layer of a thermoplastic resin and a curableresin on the carrier. The carrier may be a plastic film. The plasticfilm can be a PET film, a PP film, or a PE film. The carrier can have athickness of 15 μm or more and 200 μm or less.

The surface-relief hologram has a relief surface. The relief surface hasa surface relief with concave portions or convex portions, or concaveportions and convex portions, and exhibits optical properties such asdiffraction, light reflection suppression, isotropic or anisotropiclight scattering, refraction, polarized and wavelength-selectivereflection, transmission, and light reflection suppression. When therelief layer is provided with a diffraction grating structure regionhaving a pitch of 0.5 μm or more and 2 μm or less and a depth of 0.05 μmor more and 0.5 μm or less, for instance, the hologram exhibits theproperty of diffracting light. When the relief layer is provided with amoth-eye structure or a deep grating structure having a pitch of 0.1 μmor more and 0.5 μm or less and a depth of 0.25 μm or more and 0.75 μm orless, for instance, the surface-relief hologram exhibits the propertiesof suppressing light reflection, polarized and wavelength-selectivereflection, transmission, and light reflection suppression. When thesurface-relief hologram is provided with, for instance, an acyclic line-or dot-shaped repetitive structure region having an average pitch of 0.5μm or more and 3 μm or less and a depth of 0.05 μm or more and 0.5 μm orless, the surface-relief hologram exhibits the property of emittingisotropic or anisotropic scattered light. When the surface-reliefhologram is provided with a structure region having an average pitch oflarger than 3 μm and a depth of larger than 0.5 μm and is made differentin refractive index from the adjacent layer, the surface-relief hologramexhibits the property of refraction. The optical properties of thehologram structure can be perceived and sensed by visual inspection andmechanical detection. This improves anti-counterfeiting/tamperingperformance and appearance.

The hologram structure may have a plurality of hologram structureregions. The hologram structure region can display a single image or acombination of plural images. The image can represent a single piece oftext or a code, or a combination thereof. The code can be aone-dimensional code or two-dimensional code. Instances of theone-dimensional code include a bar code, a serial number, or acombination thereof. Instances of the two dimensional code include a QRcode and a matrix code.

In order to improve the luminance of diffraction light generated by thefine concave-convex structure formed on the hologram film, the fineconcave-convex structure on the hologram film may be covered with areflective layer. That is, the hologram structure may be covered with areflective layer. The reflective layer can cover the fine concave-convexstructure by vapor-phase deposition on the concave-convex structure. Thevapor-phase deposition can be chemical vapor-phase deposition orphysical vapor-phase deposition. As the physical vapor-phase deposition,vacuum vapor deposition or sputtering can be applied. The material forthe reflective layer can be metal oxide, metal, or silicon oxide. Themetal oxide can a metal sulfide, metal oxide, metal nitride or metalfluoride.

Instances of the metal sulfide include zinc sulfide. Instances of themetal oxide include titanium oxide, aluminum oxide, and zirconia.Instances of the metal nitride include titanium nitride. Instances ofthe metal fluoride include calcium fluoride and magnesium fluoride. Themetal can be aluminum (Al), silver (Ag), chromium (Cr), or nickel (Ni).Alternatively, the metal can be an alloy of them. The reflective layerimproves the luminance of a reconstructed image of the hologramstructure. Specifically, the reflective layer increases the luminance ofthe check data 22 displayed as a reconstructed image by the hologramstructure. This makes the authentication medium easier to verify. Theverification can be performed using an observation method and averification method described later. The reflective layer can have athickness of 10 nm or more and 500 nm or less. With a thickness of 10 nmor more, it is easy to enhance the ease of determining theauthentication medium. With a thickness of 500 nm or less, it is easy todeposit the reflective layer.

The inorganic-material reflective layer can be formed by a wet coatingtechnique such as a sol-gel process as well as the above-mentioned drycoating technique. The hologram structure may further have an adhesivelayer. The material for the adhesive layer can be acryl, polyester,urethane, or a composite, mixture, or copolymer thereof. The adhesivelayer may contain powder. The powder can be inorganic powder or polymerpowder. The adhesive layer may contain a plurality of kinds of powder.There may be an anchor layer between the adhesive layer and the hologramstructure. The material for the anchor layer can be acryl, urethane, ora composite, mixture, or copolymer thereof. The adhesive layer can bearranged on one or both surfaces of the hologram structure.

In an example according to the present embodiment, the check data 22having four numbers “9”, “8”, “7”, and “6” as information segments isdisplayed in space 23 displaying the check data 22. Therefore, thehologram structure with the four information segments 9, 8, 7, and 6 asreconstructed images is formed in the second region 12. The hologramstructure has a hologram segment where the four information segments arereproduced. Further, the hologram structure can be configured, as shownin FIG. 2B, such that respective reconstructed images 22 a, 22 b, 22 c,and 22 d of the information segments are arranged at different positionsin the thickness direction of the authentication medium 100(hereinafter, called “reproduction positions”). That is, thereconstructed images 22 a and 22 b can be reproduced under the laminatesheet 30 where the second region 12 is located, and the reconstructedimages 22 c and 22 d can be reproduced above the laminate sheet 30.

The reproduction positions of the information segments may constitute apart of the check data 22. For example, when codes 1, 2, 3, and 4 arerespectively added to the reproduction positions of the reconstructedimages 22 a, 22 b, 22 c, and 22 d, the check data 22 represented by thereconstructed images shown in FIGS. 2A and 2B can be expressed as“98761234” or “91827364”. That is, the check data 22 represented by thereconstructed images can be a string of numbers, a string of letters, ora string of combined numbers and characters.

(Method of Manufacturing the Authentication Medium)

Next, a method of manufacturing the authentication medium 100 of thepresent embodiment will be described. Known configurations of componentsmay be used in the authentication medium 100. Thus, publicly knownmethods may be used in the manufacture of the authentication medium. Theauthentication medium 100 is characterized by individual informationcontained therein. Therefore, the following description will focus onthe procedure relating to individual information.

The authentication medium 100 containing the individual information canbe a license card, an ID card, or the like. That is, the personalidentification information formed in each authentication medium 100 maybe different.

FIG. 3 is a flowchart of a procedure for forming individual informationto be added to the authentication medium 100.

First, the personal identification information 21 is acquired in stepS200. In step S200, typically, but not limited to this, the personalidentification information 21 is acquired from an application documentor an entry form on the web completed by the owner to whom theauthentication medium 100 is to be issued.

Subsequently, in step S210, the check data 22 is generated based on thepersonal identification information 21 acquired in step S200. In stepS210, hash values are obtained by a hash function from a part or all ofthe personal identification information 21 and are set as check data.

The check data may be generated by using a simple hash function. Thesimple hash function for generating the check data can be used toconvert the characters and numbers included in the personalidentification information into ASCII codes and form a number string,and divide the number string by a specific number string and set theresulting remainder as the check data. Otherwise, specific informationincluded in the personal identification information (for example, acombination of the last two digits of the birth date and the charactersof the first name, etc.) itself may be set as the check data.

The hash function can be a cryptographic hash function. As such acryptographic hash function, the Secure Hash Algorithm standardized bythe US National Institute of Standards and Technology can be applied.The cryptographic hash function can be a block cipher. Instances of thecryptographic hash function include MDS, SHA family, Whirlpool, RIPEMD,RadioGatun, bcrypt, and BLAKE2.

Upon completion of step S210, all the individual information to be addedto the authentication medium 100 is prepared. The personalidentification information 21 acquired in step S200 and the check data22 acquired in step S210 are associated with each other in a replicablemanner by the processing performed in step S210.

Subsequently, in step S220, the personal identification information 21is formed in the first region 11 of the laminate sheet 30. The formationmethod can be any of the various methods described above. Forming thepersonal identification information 21 by laser on the surface of thelaminate sheet 30 makes it hard to counterfeit the authentication medium100.

The laser can be a pulsed laser. A pulsed laser is easy to adjust inpower by varying its repetition rate. The pulsed laser can be asolid-state laser. Instances of the solid-state laser include a YVO4laser and a YAG laser. The repetition rate of the pulsed laser can befrom continuous wave (CW) to 1 MHz or less. The pulse width of thepulsed laser can be 100 microseconds to 100 femtoseconds. The personalidentification information 21 can be recorded by carbonizing a part ofthe laminate sheet 30 using a laser. Alternatively, the personalidentification information 21 can be recorded by printing with ink onthe laminate sheet 30 and discoloring the ink by laser. The ink can befluorescent ink or infrared absorbing ink. The fluorescent ink or theinfrared absorbing ink can be a dye ink or a pigment ink. Thefluorescent ink or the infrared absorption ink is an invisible ink.Invisible inks allow formation of a latent image. In other words,discoloring a part of the invisible ink makes it possible to form alatent image of the personal identification information 21 using alaser. This further improves anti-counterfeiting properties. An instanceof a visible ink is an optically variable ink. The optically variableink can be a magnetic ink. The optically variable magnetic ink makes itpossible to form a characteristic pattern using a magnetic field. Thisprevents counterfeiting because it is hard to imitate a characteristicpattern formed by such a magnetic field.

Subsequently, in step S230, the hologram structures with the check data22 as reconstructed images are formed in the second region 12 of thelaminate sheet 30. The hologram structures can be formed by selectivelytransferring information segments matching the check data from thehologram film on which the information segments are recorded in advance.

When the check data is formed of only Arabic numbers, the informationsegments of the check data are the ten digits 0 to 9. Therefore, asshown in FIG. 4A, a hologram film (hologram structure group) 150 inwhich a large number of hologram structures, having ten digits asregularly formed reconstructed images, is used, and only the digitsrequired are sequentially arranged in the second region 12. That is, thehologram film has a plurality of hologram structures. FIG. 4B is across-sectional view of FIG. 4A taken along line I-I. The five hologramstructures of the same digits aligned in the same line have respectivedifferent reproduction positions 150 a, 150 b, 150 c, 150 d, and 150 e.It is therefore possible to accommodate any of the reproductionpositions that might be set for the digits in the check data.

Instead of the hologram film 150, ten types of hologram films may beused, each having a different respective digit repeated in the hologramstructures as the reconstructed images are formed.

FIGS. 4A and 4B show the hologram film 150 with only Arabic numbers.Alternatively, the hologram film 150 may have character information.Instances of the character information include alphabetic characters andGreek characters.

To selectively transfer specific information segments to the secondregion, methods using a thermal head or a laser can be applied. Theselective transfer can be performed by forming an adhesive layer on theback surface of the hologram film 150 and melting the adhesive layeronly at the parts of the information segments to be transferred by theheat of the thermal head or the heat of the laser.

Alternatively, the selective transfer may be performed by providing anadhesive layer already exhibiting adhesion properties on the backsurface of the hologram film 150 and then removing by laser the adhesivelayer only from the region that is not a transfer target.

The method of forming the check data is not limited to those using ahologram film described above. The hologram structures may be formed byforming the generated check data on an intermediate transfer foil andattaching or laminating the foil to the second region 12. Alternatively,the hologram structures with the check data 22 as reconstructed imagesmay be formed inside the laminate sheet 30 by making portions of thelaminate sheet transparent, and then causing material modificationcorresponding to the optical phase information of the generated checkdata, inside of the transparent portions, by a pulsed laser.

FIGS. 4A and 4B show an example of the hologram film 150 on which onlythe information segments for forming the check data are formed.Alternatively, the hologram film 150 may be provided with a printedguide pattern for alignment during attachment of the informationsegments to the second region 12 or an intermediate transfer foil film.The guide pattern may be formed by a hologram structure. Instance ofguide patterns are rectangles, crosses, circles, triangles, polygons,and combinations thereof.

According to the method of manufacturing the authentication medium inthe present embodiment, the order of steps S200 to S230 described abovecan be changed unless a contradiction occurs between them. The followingchanges are possible:

-   -   Reversing the order of steps S220 and S230. In this case, the        second region may partially overlap the first region. In this        case, a track of recording the personal identification        information 21 is left on the hologram structures as well, which        prevents tampering by hologram replacement.    -   Performing step S220 before step S210.

The hologram structure may be embedded in an ID card.

In the present embodiment, in order to embed the hologram structures forreproducing the check data in the authentication medium, the hologramstructure is first transferred to the laminate sheet 30. The transfercan be done using a metallic or resin stamper. In this transfer process,as conditions for transferring the hologram structures, the surfacetemperature of the press surface of the stamper can be set to 80° C. ormore and 150° C. or less, the time during which the hologram structureis kept in contact with a transfer target can be set to 0.1 seconds ormore and 3 seconds or less, and the transfer pressure can be set to 100kg/cm² or more and 500 kg/cm² or less.

After that, a transparent cover layer is laminated on one surface of thelaminate sheet 30 with the hologram structure transferred thereto. Thematerial for the cover layer can be a thermoplastic. Since athermoplastic becomes softened by heat, the cover layer is pressedagainst the laminate sheet 30 and the hologram structures, and they aremerged by hot pressing. The merge makes it possible to cover the onesurface of the laminate sheet and coat the hologram structures. In thisprocess, the temperature of the heat source can be set to 170° C. ormore and 200° C. or less, and the time during which the heat source iskept in contact with these components can be set to one minute or moreand 30 minutes or less.

(Method of Reading the Authentication Medium)

Next, a method of reading the authentication medium of the presentembodiment manufactured as stated above will be described.

Of the individual information recorded on the authentication medium 100,the personal identification information 21 can be read by a publiclyknown reading device. This device can be a line scanner. The personalidentification information 21 can be read using a publicly known readingdevice by irradiating with light of a predetermined wavelength from apredetermined angle. However, since the check data 22 is recorded asreconstructed images of the hologram structures, the check data 22cannot be correctly reproduced unless the check data 22 is irradiatedwith light of a predetermined wavelength that is the reference light ofthe hologram structures from a predetermined angle. For example, if thecheck data 22 is irradiated with light of a wavelength different fromthe reference light, the reconstructed images are displayed but theirreproduction positions are shifted from the correct positions. Inaddition, for example, if the authentication medium is irradiated withlight from an angle different from the predetermined angle, thereconstructed images are displayed but formed at positions displacedfrom the positions read by a camera or an optical sensor.

Therefore, in the method of reading the authentication medium of thepresent embodiment, condition information indicating conditions forreading the check data is acquired (step A), the second region isirradiated with light of a predetermined wavelength at a predeterminedangle based on the condition information (step B), and the check data isread (step C).

There is no particular limitation on the mode of acquiring the conditioninformation in step A. Instances of the mode of acquiring the conditioninformation in step A include a mode in which the condition informationis included in advance in the personal identification information 21 andthen the condition information is acquired during reading of thepersonal identification information 21, a mode in which the provider ofthe authentication medium provides the condition information to thereading user in advance, and the like. In the latter case, the providerof the authentication medium may manufacture the authentication mediawhile regularly changing the condition information, and provide the userwith the condition information in association with the time ofmanufacture (which is generally synonymous with the time of issuance tothe owner). In the former case, the changed condition information isincluded in a part of the personal identification information in realtime, which saves the time and effort to provide the conditioninformation to the reading user. The condition information may beprocessed and included in the personal identification information. Theprocess may be encryption.

(Method of Verifying the Authentication Medium)

Next, a method of verifying the authentication medium according to thepresent embodiment will be described.

FIG. 5 is a flowchart showing a flow of the method of verifying theauthentication medium according to the present embodiment.

First, in step S310, the personal identification information 21 in thefirst region 11 is read. Subsequently, in step S320, the check data 22in the second region 12 is read. Steps S310 and S320 may be performed bythe method of reading the authentication medium described above.

Subsequently, in step S330, it is determined whether the check data 22acquired in step S320 corresponds to the personal identificationinformation 21 acquired in step S310, thereby determining theauthenticity of the authentication medium 100.

Some instances of step S330 will be listed below.

-   -   a. The personal identification information and the check data        are collated to verify that they are consistent. When a part of        the personal identification information itself constitutes the        check data, the check data and the part of the personal        identification information constituting the check data can be        collated and verified.    -   b. The personal identification information 21 and the check data        22 are verified from a database in which they are stored. The        database may be within the reader of the authentication medium        or may be located on a server or cloud on the internet.    -   c. The personal identification information 21 acquired in step        S310 is converted by a conversion method for generating check        data to generate check data for collation, and the generated        check data for collation and the check data 22 acquired in step        S320 are collated with each other.    -   d. The check data 22 acquired in step S320 is converted in a        reversed procedure of the conversion method for generating        second individual information, to generate personal        identification information for collation, and the generated        personal identification information for collation and the        personal identification information 21 acquired in step S310 are        collated with each other. This mode is applicable to the case        where the check data has been generated in a mode capable of        reverse conversion.

Examples c and d are advantageous in that there is no need to constructa separate database for collation, which may become very large in size.

In the verification method according to the present embodiment, theorder of step S310 and step S320 may be reversed.

(Reader)

The reader applied to the present embodiment can be a reader thatincludes a device to read the personal identification information and acomponent to read the check data such as a camera or an optical sensor.The device to read the personal identification information can be a linescanner.

As described above, the authentication medium 100 of the presentembodiment is hard to counterfeit because it includes the personalidentification information 21 and the check data 22 associated with thepersonal identification information 21. That is, even if a counterfeitertampers only with the personal identification information 21, there isan association between the tampered personal identification informationand the check data 22 so that the counterfeiting can be detected by thecollation between the personal identification information and the checkdata. Further, without knowing how the check data is generated, thecheck data corresponding to rewritten personal identificationinformation cannot be specified, and thus counterfeiting of the checkdata is effectively impossible.

Therefore, the security of the authentication medium 100 is higher thanother media with a hologram transfer foil on which a shape or patternnot associated with the personal identification information is recorded.

In addition, the check data 22 has a plurality of reproduction positionsof the information segments, which ensures variety of the check dataeven if the number of information segments is small. For example, whenthe check data is formed of three digits, there are 1000 possiblecombinations of the numbers. However, presetting five individualreproduction positions for these numbers would create 125,000 possiblecombinations, that is, over a hundred times the previous number ofcombinations.

Further, setting the difference between the reproduction positions to besmall to a degree that the reconstructed image cannot be easilyrecognized by visual inspection (for example, 1 mm or less) makes thecheck data more difficult to counterfeit because it is less likely thatcounterfeiters will recognize that a plurality of reproduction positionshave been used.

According to the method of manufacturing the authentication medium ofthe present embodiment, it is possible to mass-produce theauthentication medium 100 with different check data 22 by recordingcheck data varying in accordance with the personal identificationinformation in the hologram structures in the second region 12.

According to the method of reading the authentication medium of thepresent embodiment, it is possible to reliably read the check data usingthe condition information acquired in step A. In the method of readingthe authentication medium of the present embodiment, the authenticationmedium with condition information included in the personalidentification information is used to allow the acquisition of thepersonal identification information and condition information at thesame time, thereby improving convenience to the user.

According to the verification method of the present embodiment, theauthenticity of the authentication medium is determined based on thepersonal identification information 21 and the check data 22 recorded onthe authentication medium 100, which makes it possible to detectcounterfeited authentication media easily and reliably.

Next, experimental results of the present invention will be described.

Experimental Examples

Hologram structures were calculated such that a computer-generatedhologram reproduces uppercase alphabet characters “A”, “B”, and “C” atpositions 5 mm, 7 mm, and 9 mm, respectively, from the front side withreference to a hologram film interface, and then a hologram transferfoil with the hologram structures embossed thereon was produced. Thereference light was green light.

The produced hologram transfer foil was transferred onto a polycarbonatesheet. Another polycarbonate sheet was overlaid on the formerpolycarbonate sheet and was subjected to thermal lamination to produce alaminate sheet with the hologram structures embedded therein.

Two pieces 53.98 mm long and 85.6 mm wide of the foregoing laminatesheet were prepared (in conformity with international standardISO/IEC7810 ID-1 that prescribes identification card size), and theinformation on a fictitious person A was recorded as personalidentification information on one of the two (experimental example 1).The information on a fictitious person B was recorded as personalidentification information on the other (experimental example 2). Eachpersonal identification information was recorded on the surface of thelaminate sheet using an infrared laser with a wavelength of 1064 nm.

A reader including a full-color LED light source, an optical prism, anda CMOS sensor was prepared. When the authentication medium was set onthe reader, the light emitted from the light source vertically enteredthe authentication medium, and the reconstructed images of the hologramstructures were formed on the CMOS sensor. Only the reconstructed imagesat the corresponding reproduction positions can be selectively acquiredby changing the installation position (imaging condition) of the CMOSsensor.

When the authentication media of experimental examples 1 and 2 wereirradiated with green light, the reconstructed images “A”, “B”, and “C”were reproduced at the positions 5 mm, 7 mm, and 9 mm, respectively, onthe front side of the hologram transfer foil interface.

When the authentication media of experimental examples 1 and 2 wereirradiated with red light, the reconstructed images “A”, “B”, and “C”were reproduced at the positions 3 mm, 5 mm, and 7 mm, respectively, onthe front side of the hologram transfer foil interface. That is, thereproduction positions of the hologram structures varied depending onthe wavelength of the light emitted from the light source.

When the conditions for verification are “green light, 7 mm from thefront side”, the check data in the experimental examples is “B”. Thatis, the reconstructed images “A” and “C” are dummy reconstructed imagesnot constituting check data. When the conditions for reading by thereader (the emission light wavelength and the installation position ofthe CMOS sensor) coincide with the condition information, the readeracquires only the correct check data “B”. When the reading conditionsare different from the condition information, the reader cannot acquirethe correct check data. For example, when the reading conditions are“red light, 7 mm from the front side”, the reader acquires only thereconstructed image “C”. When the reading conditions are “green light, 3mm from the front side”, the reader cannot acquire any reconstructedimage.

When a person attempting to counterfeit or tamper with the objectvisually checks the authentication medium of each experimental example,they can visually recognize all the reconstructed images “A”, “B”, and“C”. Thus, a person attempting to counterfeit or tamper with the objectcannot know whether the reconstructed images “A”, “B”, and “C” are allcheck data or only some of them are check data. Even if a person knowssome of the conditions (for example, the reference light is greenlight), all the reconstructed images “A”, “B”, and “C” are visuallyrecognizable under green light and thus it is not possible to correctlycounterfeit or tamper with the check data without the information on thereproduction positions which are part of the verification conditions.

As stated above, each authentication medium of the present invention ishighly resistant to counterfeiting and tampering, whereas the check datacan be easily acquired from the authentication medium by a reader andverified only if the correct condition information is known.

These conditions are changeable. For example, when the conditions are“green light, 7 mm and 9 mm from the front side”, the check data is “Band C”. When the conditions are “green light, 7 mm from the front side,and red light, 3 mm from the front side”, the check data is “A and B”.In this manner, the conditions may include reference light information,reproduction positions, or both.

Embodiments and experimental examples have been described in detail sofar with reference to the drawings. However, specific configurations arenot limited to these embodiments and experiments. The configurations ofembodiments of the present invention can be changed or combined. Thecombinations of embodiments can produce synergetic effects. Somemodifications will be shown below, but other modifications are alsopossible. Two or more of these modifications may be combined.

The check data may not include a plurality of reproduction positions.That is, the information segments in the check data may havereconstructed images reproduced at the same height.

The personal identification information and the check data may be formedon different surfaces of the laminate sheet. For instance, the personalidentification information may be recorded on the front surface of thelaminate sheet, and the check data may be formed on the back surface ofthe laminate sheet. In this configuration, in the event of damage incounterfeiting or imitation of the authentication medium, either thepersonal identification information or the check data will be affected.Therefore, the authentication medium can be easily verified.

The hologram structure described above may have a shape 501 displaying asymbol using seven segments (7-segment display) as shown in FIG. 6 ormay have a shape 502 displaying a symbol using 16 segments (16-segmentdisplay) as shown in FIG. 7 . That is, the hologram structure may be acombination of multiple holographic segments. In this case, thereflective layer can be removed (demetallized) from the hologramstructure regions corresponding to the holographic segments inaccordance with the numbers or characters to be displayed, therebyeasily making the reconstructed images of the hologram structuresresponsive to the number, character, or symbol information to berecorded. The number of holographic segments is not limited to the onesdescribed above. The hologram structure may have a 14-segment displayshape.

FIGS. 6 and 7 show each segment as a structural unit has a polygonalshape, but each segment may have a shape with corners rounded. FIGS. 6and 7 show gaps between the segments, but these gaps may not beprovided. In the case of providing gaps, all the gaps may be identicalor different in dimension. For example, the part where two segments areadjacent appears to be dark in the reconstructed image and thus thedistance between these segments is shortened, whereas the part wherethree segments are adjacent appears to be bright in the reconstructedimage and thus the distance among these segments is lengthened, wherebythe reconstructed images can be optimized.

When there is no gap between the segments, the reflective layer may bepartially removed in the adjacent unit cell regions, but thisreconstructed image has little effect on the appearance of thereconstructed images.

Each of the segments shown in FIGS. 6 and 7 may be formed of a pluralityof dot-like segments. There are no limitations on the number and shapeof the segments as far as the numbers, characters, or symbols recordedon the hologram structures can be visually recognized as reconstructedimages. The reflective layer can be partially removed from the hologramstructures, and a code can be recorded in these parts. In this case, thehologram structures may have holographic segments. Each holographicsegment, as a one-bit segment, can have a 0 or 1 recorded as data,depending on the presence or absence of the reflective layer.Specifically, the holographic segment with the reflective layer can havea 1 as data, and the holographic segment from which the reflective layerhas been removed can have a 0 as data. Conversely, the holographicsegment with the reflective layer can be set to 0, and the holographicsegment from which the reflective layer has been removed can have a 1 asdata. Otherwise, the code may be recorded depending on the presence orabsence of the reflective layer, not in conjunction with the hologramstructures. In this case, when the reflective layer is to be removedfrom the hologram structures by laser, the relative positions of theremoval positions and the hologram structures may be only approximatelydetermined.

FIGS. 8 and 9 each show an example of hologram structure arrangementwhere a reconstructed image of a hologram structure is formed of sevensegments. Referring to FIG. 8 , a plurality of unit cell regionsarranged in a two-dimensional matrix is set as one segment. A segment511 shown in FIG. 8 is formed of seven unit cell regions 520. The entirehologram structure can have an outer shape of a square as shown in FIG.8 by arranging the segments without a gap therebetween while changingthe shape of each segment and the number of unit cell regions.

Each unit cell region 520 can have one side of 20 μm or more and 300 μmor less. The size of the unit cell region 520 can be a size of a squarecircumscribing a unit cell region 520. This makes each unit cell regionhard to observe by visual inspection.

FIG. 9 shows an example in which each segment is formed of one unit cellregion 521. The unit cell region shown in FIG. 9 is larger than the unitcell region shown in FIG. 8 . In this example, alignment duringdemetallization becomes easy.

The size of the unit cell region 521 can be 100 μm or more and 300 μm orless, for instance. The size of the unit cell region 521 can be the sizeof a square circumscribing the unit cell region 521. The unit cellregion may have a size capable of visual recognition. When the unit cellregion is large, forming the reflective layer from a light-permeable,highly refractive material makes it hard to recognize the removal of thereflective layer by visual inspection, thereby improving the appearance.

As another example, FIG. 10 shows an arrangement example of unit cellregions 522 in a hologram structure 503 corresponding to a 16-segmentdisplay shape.

A plurality of holographic segments may be arranged with a gap lefttherebetween. When a plurality of holographic segments are arrangedwithout a gap therebetween, there can exist a region where minutehologram structures constituting the holographic segments are mixed toobscure the boundaries between the holographic segments.

In the shape 501 shown in FIG. 6 or the shape shown in FIG. 9 , when thereflective layer is not removed from any of the segments, the segmentsare visually recognized as number “8”. As shown in FIGS. 11 and 12 ,removing the reflective layer from predetermined segments Sd bydemetallization allows the segments to be visually recognized as number“2”. In this way, removing the reflective layer from unit cell regionsconstituting a predetermined segment makes it possible to form areconstructed image on demand.

The reflective layer may be fully removed from the segments to besubjected to demetallization. In this case, it is easy to enhance thevisual recognition of the check data 22 displayed by the hologramstructure. Otherwise, only a part of the reflective layer may beremoved. In this case, it is easy to improve the speed of recording thecheck data 22 on the hologram structure. Even in this case,demetallization can be performed to such a degree that the difference inbrightness between the segments having undergone demetallization and thesegments not having undergone demetallization can be visuallyrecognized. In the case of removing only a part of the reflective layer,the removed region may form a linear pattern, characters, numbers, afine pattern, or a geometric pattern. In this case, authenticityverification can be performed by checking whether the removed regionforms a predetermined pattern by observation under magnification.

As shown in FIG. 13 , reconstructed images Im may be reproduced atdifferent positions among a plurality of hologram structures (see thecross-sectional view on the bottom). In this case, the reproductionpositions can be added as information as well as the numbers orcharacters formed on demand. As a result, a large quantity ofinformation can be added on demand.

The reproduction positions of the reconstructed images may be variedregularly. Further, the reproduction positions of the reconstructedimages may be varied monotonically. The monotonic varying in thereproduction positions can be monotonic separation from or approach tothe hologram structures. This monotonic varying in the reproductionpositions makes it easy to detect the replacement of the positions inthe hologram structures. In the example of FIG. 13 , a shift to becomegradually shallower in depth from left to right among the reproductionpositions can be seen. On the other hand, the reproduction positions maybe varied at random in a non-monotonic manner. The non-monotonic variesin the reproduction positions can be regular varying or random varying.In one hologram structure, the segments may be reproduced at differentpositions.

One demetallization method is laser ablation. In removal (ablation) ofthe reflective layer using a laser, the condensing diameter of the laserand a distance G between the outer edge of a region R1 where acomputer-generated hologram structure is formed in each unit cell regionand an outer edge P1 of the unit cell region (see FIG. 14 ) contributeto the accuracy of alignment during ablation.

At the time of laser ablation, since the laser is condensed and applied,the removed area is circular in shape. Therefore, when the distance G isshort, the reflective layer is not fully removed from the region R1 butis left at the four corners as shown in FIG. 15 . From the viewpoint ofpreventing this phenomenon, the distance G can be made identical to orgreater than the laser spot diameter. Further, the distance G may betwice as large as the condensing diameter. Moreover, the distance G maybe 100 times or less as large as the condensing diameter of the laser.

Alignment marks may be provided to increase the accuracy of alignmentduring laser ablation. The alignment marks can be formed by a hologram,a diffraction grating pattern, or printing.

The pattern width of the reflective layer to be removed by laserablation can be in the range of 1 μm or more and 100 μm or less. Apattern width of 1 μm increases the resolution of the hologram structuredisplaying information. A pattern width to 100 μm or less enhances theease of laser processing.

The intensity of light from a reproduction light source for reproducingeach segment may be uniform in the entire segment or may be differentamong the parts of the segment. Increasing the intensity of light fromthe reproduction light source at the central part of each segment anddecreasing the intensity of light from the reproduction light source atthe peripheral part of each segment obscures the boundary betweenadjacent segments and suppresses a reduction in the quality of thereconstructed image that might be caused by the demetallization of thereflective layer. In contrast, decreasing the intensity of light fromthe reproduction light source at the central part of each segment andincreasing the intensity of light from the reproduction light source atthe peripheral part of each segment makes it possible to enhance thevisual recognition of the segments.

The density of light from the reproduction light source may be variedcontinuously or intermittently.

The area where a hologram structure is to be provided in a unit cellregion can be set in accordance with the reconstructed image. As shownin FIG. 16 , providing a hologram structure Ch in an entire unit cellregion 530 makes the reconstructed image brightest. On the other hand,when the authentication medium is observed from a certain angle, a partof the segment may appear to be lost depending on the reproductionposition of the reconstructed image, particularly a reproductionposition along the thickness direction of the authentication medium.

Forming a void area without a hologram structure at both horizontalsides of the unit cell region 530 as shown in FIG. 17 or forming a voidarea Sp at both vertical sides in the unit cell region 530 as shown inFIG. 18 makes it possible to control the viewing angles in thereconstructed image in the vertical and horizontal directions andsuppress the reconstructed image of the holographic segment fromappearing to be partially lost at some observation angles.

The void regions Sp may be formed by demetallization of the reflectivelayer.

The reflective layer can be formed from a metallic material, metaloxide, metal sulfide, or a combination of them. Forming the reflectivelayer from these materials increases the reflectance from the hologramstructure and makes the reconstructed image brighter. In particular,with the reflective layer formed from a transparent metal oxide or metalsulfide, the authentication medium can be used in fields in whichtransparent authentication media such as personal authentication cardsare required.

The reflective layer can be formed from a metal oxide or metal sulfidewith the property of absorbing a laser wavelength to be used so that themetal oxide or metal sulfide can be removed by laser abrasion.Otherwise, laser abrasion can be performed even on a metal oxide ormetal sulfide without the property of absorbing that laser wavelength,by applying specific wavelength absorbing ink near the reflective layer.The laser for laser abrasion can be a solid-state laser. Instances ofthe solid-state laser include a YVO4 laser (with a wavelength of 1064nm) and a YAG laser (with a wavelength of 1064 nm). In this case, as thespecific wavelength absorbing ink, infrared absorbing ink may be appliednear the reflective layer. This facilitates improvement of the scanningspeed of the laser.

In the case of using a metallic material for the reflective layer, afine concavo-convex structure of the hologram film with a fineconcavo-convex structure formed thereon may be partially covered withthe reflective layer of the metallic material. The reflective layer maybe wire-like patterned. The wire-like pattern may be a mesh-likepattern. By partially covering the fine concave-convex structure withthe reflective layer of the metallic material, the information printedon the personal authentication card covered with the fine concave-convexstructure can be visually recognized without being concealed by theauthentication medium. At the same time, patterning by laser ablation ispossible because the partially remaining metallic material absorbs thelaser light. The mesh structural scale can be in the range of 10 μm ormore and 300 μm or less, more specifically in the range of 10 μm or moreand 100 μm or less. Within this range, the presence of the metallicmaterial can be made hard to recognize during visual inspection andobservation.

The reproduction position of a reconstructed image may be varied in adirection other than the depth direction described above. In the exampleshown in FIG. 19 , a reconstructed image Im is reproduced at a positionseparated from a hologram structure 540 not in a normal direction to thehologram structure 540 but in a direction at an angle θ formed withrespect to a normal N. As a result, the reconstructed image Im isshifted upward (in a y-axis positive direction shown in FIG. 19 ) fromthe hologram structure 540.

By appropriately shifting the reproduction position, the reconstructedimage Im can be easily observed and the visibility is improved. Theshift direction is not limited to the upward direction but can be set tothe downward direction, the horizontal direction (x-axis direction inFIG. 19 ), or a diagonal direction. The amount of the shift can also beset.

In the example shown in FIG. 20 , a reconstructed image and a hologramstructure are non-parallel to each other. That is, a distance D1 betweenthe reconstructed image Im and the hologram structure 540 at the lowerend of the reconstructed image Im is shorter than a distance D2 betweenthe reconstructed image Im and the hologram structure 540 at the upperend of the reconstructed image Im, so that the distance between thereconstructed image Im and the hologram structure 540 gradually becomeslonger toward the upper end. Changing the distance between thereconstructed image and the hologram structure at each part of thereconstructed image makes it possible to add dynamic motion to thereconstructed image and facilitate visual recognition by the user. Thedirection and amount of change in the distance can be within specificranges.

The information regarding the reproduction position can be favorablyused as key information for offline authentication by visual inspection.

Embodiments of the present invention have been described so far withreference to the drawings. However, specific configurations of thepresent invention are not limited to these embodiments. The presentinvention can include designs within the scope of the present inventionand all embodiments that produce effects equivalent to those of thepresent invention.

Furthermore, the scope of the present disclosure should not be limitedto the features of the invention defined by the claims, but should alsoinclude all the disclosed features and all the combinations of thefeatures.

The terms “part”, “element”, “region”, “segment”, “unit”, “printedmatter”, and “article” used in the present disclosure denote physicalexistence. Physical existence can refer to a substantial form or aspatial form surrounded by objects. The physical existence can be astructure. The structure may have specific functions. A combination ofstructures having specific functions can produce synergistic effects bya combination of the functions of the structures.

The terms used in the present disclosure and, particularly, in theclaims (for example, the text of the claims) are generally intended as“open” terms (for example, the term “have” should be interpreted as “atleast have”, and the term “include” should be interpreted as “include,but not be limited to”, or the like).

The terms, configurations, features, aspects, and embodiments should beinterpreted with reference to the drawings as necessary. Matters thatcan be directly and unambiguously derived from the drawings shouldprovide the basis of amendment as the text of the specification does.

If the introduction of a specific number in the claims is intended, suchan intention will be clearly specified in the claims. If there is notsuch a specification, the intention does not exist. For example, for thesake of clarity, the appended claims can use introductory phrases, suchas “at least one” or “one or more”, in the claim recitation. However,the use of such phrases should not be construed to imply that theintroduction of a claim recitation by the indefinite articles “a” or“an” limits any particular claim containing such claim to embodimentscontaining only one such recitation. The introductory phrase “one ormore” or “at least one” and the indefinite article “a” or “an” (e.g.,“a” and/or “an”) should be at least interpreted as meaning “at least oneor more.” That is, “one” or “one or more”). The same applies to the useof definite articles, which are used for introduction of claimrecitation.

INDUSTRIAL APPLICABILITY

The present invention is applicable to authentication media.

REFERENCE SIGNS LIST

-   -   11 . . . First region; 12 . . . Second region; 21 . . . Personal        identification information; 22 . . . Check data; 22 a, 22 b, 22        c, 22 d . . . Reconstructed image; 23 . . . Space; 30 . . .        Laminate sheet; 100 . . . Authentication medium; 150 . . .        Hologram film (hologram structure group).

What is claimed is:
 1. An authentication medium, comprising: asheet-like laminate sheet; a first region that is formed on the laminatesheet and in which personal identification information is recorded; anda second region that is formed on the laminate sheet and has a hologramstructure in which check data associated with the personalidentification information is recorded, wherein the check data has aplurality of information segments, and the hologram structure is acombination of a plurality of hologram segments that reproduces theplurality of information segments and wherein respective reconstructedimages of information segments of the plurality of information segmentsare arranged at different positions in a thickness direction of theauthentication medium.
 2. The authentication medium of claim 1, whereinthe check data is hash data of the personal identification information.3. The authentication medium of claim 1, wherein the check data isformed from a part of the personal identification information.
 4. Theauthentication medium of claim 1, wherein the second region overlaps allor part of the first region in a planar view of the authenticationmedium.
 5. The authentication medium of claim 1, wherein the personalidentification information is formed on a surface of the laminate sheet.6. The authentication medium of claim 1, wherein at least one of thepersonal identification information and the hologram structure is formedinside the laminate sheet.
 7. A method of reading the authenticationmedium of claim 1, comprising: a step of acquiring condition informationindicating a condition for reproducing the check data from the hologramstructure of the authentication medium; and a step of irradiating thehologram structure with light based on the condition information, tothereby reproduce the check data.
 8. The authentication medium readingmethod of claim 7, further comprising a step of reading the personalidentification information recorded on the authentication medium,wherein the personal identification information includes the conditioninformation.
 9. An method of verifying authenticity of theauthentication medium of claim 1, comprising: a step of reading thepersonal identification information recorded on the authenticationmedium; a step of reading the check data recorded on the hologramstructure of the authentication medium; and a step of determining theauthenticity of the authentication medium, based on the read personalidentification information and the read check data.
 10. Theauthentication medium verification method of claim 9, wherein theauthenticity of the authentication medium is determined based on theread personal identification information, the read check data, and areproduction position of the check data.
 11. The authentication mediumof claim 1, wherein a reconstructed image of each information segment ofthe plurality of information segments is arranged at a position in thethickness direction of the authentication medium, which is differentthan a position in the thickness direction of the authentication mediumof a reconstructed image of any other information segment of theplurality of information segments.
 12. The authentication medium ofclaim 1, wherein respective reconstructed images of information segmentsof the plurality of information segments include a first reconstructedimage of a first information segment of the plurality of informationsegments and a second reconstructed image of a second informationsegment of the plurality of information segments, wherein the firstreconstructed image is reproduced under the laminate sheet in thethickness direction of the authentication medium and the secondreconstructed image is reproduced above the laminate sheet in thethickness direction of the authentication medium.
 13. An authenticationmedium manufacturing method, comprising: a step of acquiring personalidentification information; a step of generating check data associatedwith the personal identification information, based on the personalidentification information; a step of selecting a hologram segmentrepresenting at least a part of the check data, from a hologramstructure group; and a step of transferring the selected hologramstructure onto a laminate sheet, wherein the check data has a pluralityof information segments, and the hologram structure is a combination ofa plurality of hologram segments that reproduces the plurality ofinformation segments and wherein respective reconstructed images ofinformation segments of the plurality of information segments arearranged at different positions in a thickness direction of theauthentication medium.
 14. The authentication medium manufacturingmethod of claim 13, wherein the check data has a plurality ofinformation segments, and the hologram structure is a combination of aplurality of hologram segments that reproduces the plurality ofinformation segments.